Answer:
See below.
Step-by-step explanation:
What you wrote means:
[tex] r = \dfrac{n}{2}(b + H) [/tex]
If that is what you meant, then the answer is:
[tex] \dfrac{2r}{n} = b + H [/tex]
[tex] H = \dfrac{2r}{n} - b [/tex]
On the other hand, if this is what you meant:
[tex] r = \dfrac{n}{2(b + H)} [/tex]
then the answer is:
[tex] 2r(b + H) = n [/tex]
[tex] 2rb + 2rH = n [/tex]
[tex] 2rH = n - 2rb [/tex]
[tex] H = \dfrac{n - 2rb}{2r} [/tex]
